The invention generally relates to a redundant power subsystem, such as a system to power a server, for example.
A typical computer system includes a power subsystem that provides and regulates various supply voltages that are used by and power the components of the computer system. As examples, the power subsystem may provide and regulate supply voltages for 5 volt (V), 3.3 V, 2.5 V, 1.8 V and 1.5V power planes (also called rails or voltage supply lines) of the computer system.
The power subsystem may include a full-wave bridge rectifier to convert an AC wall voltage into a voltage waveform that has a DC component. DC-to-DC voltage regulators of the power subsystem may convert this DC voltage to lower DC output voltages.
One type of voltage regulator is a switching regulator that is often chosen due to its small size and efficiency. The switching regulator typically includes one or more switches that are rapidly opened and closed to transfer energy between an inductor (a stand-alone inductor or a transformer, as examples) and an input terminal of the regulator in a manner that regulates its output voltage(s). The switching voltage regulator may be contained in a semiconductor package called a voltage regulator module.
Some computer systems, such as servers, may receive power from two AC power lines that provide two AC wall voltages, such as two 220 volt wall voltages. A purpose of this arrangement is to continue supplying power to a server system once one of the two AC wall voltages drops below a specified at which voltage regulator modules that are coupled to the corresponding AC power line may no longer be operational. For purposes of anticipating this condition, voltage regulator modules of the power subsystem may be connected to both AC power lines to implement a redundant scheme (a scheme that is often called a xe2x80x9c2 plus 2xe2x80x9d scheme).
For example, if the power subsystem needs at least two operational voltage regulator modules to power the computer system, then two voltage regulator modules may be coupled to one AC power line, and two other voltage regulator modules may be coupled to the other AC power line. In this manner, if both power lines are providing sufficient AC wall voltages, then four voltage regulator modules power the computer system. However, if one AC wall disappears, two (the minimum number) of the voltage regulator modules still provide the required power.
Each voltage regulator module may contribute significantly to the cost and size of the computer system. Thus, a difficulty with the above-described redundant system is that four voltage regulator modules are used, when only two of the voltage regulator modules are needed at any one time.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.